Vegetable oil is one of the most important primary foods. Current production of edible soybean oil in the United States is approximately 9.5 billion pounds. A typical refinery for food production requires the oil to be degummed, deacidified, bleached and deodorized. Production of refined oil can also be used as biodiesel feedstock.
Two processes have been used in refining vegetable oils and fats; chemical refining and physical refining. The decision as to which process is to be used depends on the type and quality of crude oil to be processed. Chemical refining requires less capital cost than physical refining, where the free fatty acids of the crude oils are neutralized with caustic soda. The resulting sodium soaps or soapstocks are separated by using centrifugal separators. The neutral oils are subsequently bleached and deodorized. In physical refining, the free fatty acids are removed by distillation in one stage during deodorizing. A fundamental criteria for using this method is that the crude oil be degummed as effectively as possible. This method does not produce soapstocks and thus does not require the costly soapstock splitting process. Whichever process is used, distillation is a critical step.
Distillation removes free fatty acids from the vegetable oils. During distillation, live steam is passed through the vegetable oil while it is maintained under a high vacuum and at elevated temperatures. The temperature usually ranges from 460° to 530° F. and the vacuum is maintained at 4 to 6 mm. Hg. The process may require from one and a half to seven hours. During the process most of the free fatty acids remaining in the vegetable oil are distilled off. Most of the remaining pigment products are destroyed during this step as well. The acid value and color of the oil are thus improved, and the odor and flavor are made acceptable.
Over time these distillation systems become fouled and need to be cleaned several times per year. The typical cleaning method involves an extended shutdown of the system for manual scraping. In addition to complete shutdown of the refinery, manual scraping requires confined space entry and its associated hazards. Sometimes biodiesel is then flushed through the system to remove residual soils, usually with unsatisfactory results. Other cleaning methods include use of aqueous solutions. While these can be effective, it takes a considerable amount of time to evacuate all the water out of the system before re-starting production. Any water left in the system can heat and pose a fire hazard.
As can be seen, there is a need in the art for an effective non-aqueous cleaner that can reduce manual labor, improve safety, reduce downtime and consequently increase production time and throughput.